As you already know, I'm a hand luggage only person for lots of good reasons that you can see here.
Every airline has different dimension and weight maximums for hand luggage. It's important to check what the dimensions and weight are before you head to the airport.
I also recommend travelling with a bag that is as unusual as possible. If you have a neon green bag you can spot it from a mile away, it is unlikely that someone will mistake it for theirs and walk away with it. It's also far less likely to get stolen for the same reason. No thief wants to nick a bright pink bag with black zebra stripes.
Recently the zipper on my bag broke and my husband bought me a navy blue carry on that is just like everyone else's. Noooo! That's not what we want. So I bought some kid's stickers and covered my bag with flowers. No one will mistake my bag for theirs.
Weight is another factor to take into consideration when packing your bag. Every airline has different weight limits so take the time to read through their small print carefully. I find keeping within the weight limit is harder than working with a small bag because I always carry a laptop and various plugs and chargers with me and they weigh a lot!
To solve this problem I throw all those heavy things in a backpack. That backpack functions as my purse. Airlines never weigh a purse. In fact, my purse probably weighs the same as my bag because it is carrying my liquids and my makeup pouch as well! And if I'm really unlucky and the flight personnel decide that there is no room in the overhead and tag my bag to go down into the hull, at least I will have my laptop with me--no chance it will get lost.
1) When selecting a new carry on bag, be sure it has wheels that roll in all directions
2) be sure it has a handle on the side as well as the top because if you have to carry it up stairs, it's much easier if you are lifting it from the side and not the top.